The detection of yet more alcohol in a giant molecular cloud near the centre of our galaxy could give clues to the origin of complex organic molecules in space.

Astronomers have long been seeking evidence of this particular alcohol to help explain how these life-promoting substances got started.

"The discovery of vinyl alcohol is significant," said Barry Turner, one of the staff scientists at the US National Radio Astronomy Observatory who made the discovery.

"It gives us an important tool for understanding the formation of complex organic compounds in interstellar space," he said. "It may also help us better understand how life might arise elsewhere in the cosmos."

Galactic heart

Vinyl alcohol, actually a non-inebriating complex organic molecule, is an important part of many chemical reactions on Earth, and the last of the three stable members of the C2H4O group of molecules to be discovered in interstellar space.

It was detected in a massive molecular cloud called Sagittarius B2, located 26,000 light-years from Earth, near the centre of our galaxy.

The National Radio Astronomy Observatory in Charlottesville, Virginia

Astronomers already know that there are 10 billion, billion, billion litres of methanol and ethanol in the Sagittarius B2 cloud.

The specific radio signature of vinyl alcohol was first detected using a 12-metre radio telescope during May and June of 2001. Results from the observations will soon be published in Astrophysical Journal Letters.

Of the approximately 125 molecules so far detected in interstellar space, scientists believe that most are formed by a simple process in which smaller molecules (and occasionally atoms) stick together after they collide.

But this process cannot explain how vinyl alcohol and other complex chemicals are formed in detectable amounts.

"It has been an ongoing quest to understand exactly how these more complex molecules form and become distributed throughout the interstellar medium," said Barry Turner.

Dust to dust

Since the 1970s, scientists have speculated that molecules could form on the microscopic dust grains that drift in interstellar clouds.

These dust grains are thought to trap the fast-moving molecules. The surface of these grains could act as a catalyst enabling the chemical reactions that form vinyl alcohol and other complex molecules.

The problem with this theory, however, is that the newly formed molecules would remain trapped on the dust grains by the low temperature of most of interstellar space.

The energy needed to knock them off into space where they could be detected would also be strong enough to break the chemical bonds that formed them.

Turner and others speculate that since this cloud lies near an area where young stars are forming, the energy from these stars could evaporate the icy surface layers of the grains.

This would liberate the molecules from their chilly nurseries, depositing them into interstellar space where they can be detected by sensitive radio antennae on Earth.